Non-linear video editing systems are known and include systems manufactured by AVID, Quantel and other and the SOFTIMAGE | Eddie system sold by the assignee of the present invention. Non linear video editing systems allow a user to join, manipulate and/or modify digital or digitized information from various video sources to create a finished work for rendering to an appropriate storage media or output. The sources generally need not be accessed in a linear manner and are instead accessed as required, i.e.—the last three seconds of a ten second video clip can be accessed without accessing the first seven seconds or individual video frames can be accessed and/or combined as desired. Non-linear audio editing systems are also known and allow a user to select, join, manipulate and modify digital or digitized audio sources within imposing linear access requirements.
For example, a non-linear video editor can be used to construct the video portion of a television advertisement for a new model of a car, by connecting digitized video clips of the new car driving on a country road, digital video clips of a driver in the car and digitized video clips of the car in a wind test tunnel with engineers standing about it. A non-linear audio editor can be used to create an audio soundtrack for the advertisement, comprising a selection of classic music mixed with a narrator's voice-over discussing the features of the car. The audio and video edits are then rendered to an appropriate sink, such as a VTR, RAID array, or a monitor, to obtain the finished commercial.
For the video edit, the user of the editor selects the desired video sources, their duration and order and the types of transitions between them (fades, dissolves, wipes, blends, etc.). A similar process is followed for the audio edit.
Generally, when an edit is created with such systems, a data structure or file is produced which represents the edit and defines hows the sources, such as CD's or file storage systems and linear sources, if present, such as CD's and VTR's; functions, such as dissolves, wipes, etc.; and sinks, such as DAT's, VTR's, CD-R's, file storage systems etc. are to be manipulated to render the edit. Depending upon the edit and the edit system, it may be required to ‘render’ the edit to a sink for subsequent playback or the edit may be run in real time.
Problems exist with the prior art non-linear editing systems of which the present inventors are aware. For example, in many systems of which the inventors are aware, video and audio edits are performed with separate editors, or in separate edit modules which may have different and/or inconsistent user interfaces. Further, in some systems it is difficult or onerous to insert a clip into an edit, if subsequent clips are to be displaced along the edit.
Perhaps more troubling is the fact that prior art systems may include a variety of redundant entries in the data structure or file which represents the edit, thus utilizing memory and/or system capacity which would otherwise not be required for the edit. Also, in the prior art systems it is difficult to determine if an edit which has been created can be rendered in real time or whether portions of the edit must be pre-rendered. In this latter case, it can be required that the user of the editor determine which portions of the edit should be pre-rendered.
It is therefore desired to have a non-linear editing system which can operate on both video and/or audio information with a consistent user interface, a system which can determine relatively simply and effectively whether a edit can be performed in real time and a system which makes reasonably efficient use of the memory and hardware available to the editing system.